1. Field of Invention
The present invention relates generally to molding processes. More particularly, the present invention relates to a continuous injection molding process for plastic materials.
2. Description of the Related Art
The use of plastic materials is prevalent due, at least in part, to the strength, weight, and versatility of plastic materials. In order to facilitate the use of plastic materials, extrusion technology and injection molding techniques are often used to shape plastic materials. Extrusion technology is suitable for producing extended lengths of profile shapes such as hollow core shapes. That is, extrusion technology may be used to produce extended lengths or plastic material with a substantially constant cross section. Injection molding, on the other hand, is suitable for producing discrete, three-dimensional shapes.
When extended lengths of discrete three-dimensional shapes are to be produced, a strip of plastic formed using extrusion technology may essentially be xe2x80x9cpunched out,xe2x80x9d e.g., die cut, in the strip of plastic. When material is to be punched out of a strip such that three-dimensional shapes are formed in the strip, the thickness of the strip is typically constrained. Generally, the thicker the strip the higher the probability that the quality of three dimensional shapes formed in the strip will be compromised. In other words, punching out material from a strip of plastic to form three-dimensional shapes may result in the inaccurate formation of the three-dimensional shapes.
Lengths of three-dimensional shapes may also be formed using conventional injection molding techniques. When three-dimensional shapes are formed using an injection molding process, although there is typically no thickness limitation for the width and the height of the shapes, the injection molding process is generally constrained by length. The length of an injection molded strip typically may not exceed approximately several feet, due to constraints associated with injection molding equipment and the high cost of the injection mold. Specifically, the size of the equipment used in an injection molding process, as well as the cost of the process, increases as the length of a strip produced using the process increases. Hence, when injection molding is used to form a relatively long strip of three-dimensional shapes, the shorter strips must typically be assembled together to form a longer strip.
While extrusion technology is suitable for use in the formation of long strips of material, and injection molding is suitable for use in the formation of three dimensional shapes in short strips of material, neither extrusion technology nor injection molding are particularly suitable to the formation of long strips of material of substantially any thickness that contain three-dimensional shapes. Therefore, what is needed is a method for forming long strips of material with three-dimensional shapes. That is, what is desired is a method of forming strips of material that have substantially any thickness, width, and length, and are, further, of a non-constant cross-section.
The present invention relates to forming continuous lengths of material with non-uniform cross-sections. In accordance with one aspect of the present invention, a method for forming a continuous length of material that is of a substantially non-constant cross-section includes providing the material to a single shaping wheel. The material is in a first state, and the single shaping wheel includes a template that is arranged to form a three-dimensional shape using the material. The method also includes shaping the material to form an extended strip from the material, as well as at least one three-dimensional shape in the extended strip. The extended strip and the three-dimensional shape being formed using substantially only the single shaping wheel.
In one embodiment, the method includes cooling the extended strip by cooling the material from a molten state to a solid state. In such an embodiment, the method may also include removing the cooled extended strip from the single shaping wheel, and passing the cooled extended strip over a reshaping wheel to remove any curvature from the cooled extended strip.
Forming a continuous, or extended, length of material with three-dimensional shapes thereon using a method of the present invention enables the length of material to be formed with substantially any suitable thickness, e.g., a thickness of greater than approximately one-eighth of an inch. Further, the length of the material may be substantially any length. In theory, an xe2x80x9cinfinitexe2x80x9d length of material may effectively be formed.